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In recent years, superconducting tunnel junctions have become a viable technology for a range of cryogenic applications. Superconducting tunnel junction — also known as a superconductor–insulator–superconductor tunnel junction (SIS) — is an electronic device consisting of two superconductors separated by a thin layer of insulating material. Current passes through the junction via the process of quantum tunneling. These devices have a wide range of applications, including high-sensitivity detectors of electromagnetic radiation, magnetometers, high speed digital circuit elements, and quantum computing circuits. Normal-insulating-superconducting (NIS) junctions have been used as on-chip quantum refrigerators and more recently as bulk cryogenic coolers. Both SIS and NIS technologies require pristine dielectric barriers limited to a thickness of a few nanometers. These barriers are typically fabricated using thermal oxidation of Al or Al alloys using a controlled combination of temperature, partial pressure of oxygen, and time. Unfortunately, the diffusive nature of thermal oxidation can lead to point defects in the tunnel barrier that affect junction quality and limit device performance.